Earlier today I talked about SQL Server and Dynamic Memory. What about Exchange? Not surprisingly, the Exchange group do not recommend Dynamic Memory being enabled for virtual machines that are running Exchange. You can get the official text on TechNet under the heading of Dynamic Memory Allocation Considerations. They say: “… for virtual machines that are running Exchange in a production environment, it is best to turn off memory oversubscription or dynamic memory allocation. Instead, configure a static memory size …”.
I’ve heard several times, but not seen any official text, that the Mailbox role does not support Dynamic Memory. I’m not an Exchange person (I’ve had the “luck” of usually working in sites that use Lotus Domino/Notes) but I believe that Dynamic Memory would cause problems for the Mailbox role. I have read that it only checks for available memory at start up, grabs what it can, and that’s it. Adding memory afterwards to deal with memory pressure would be pointless. Anyway, the Exchange group don’t recommend enabling DM on your Exchange VMs.